Probing proton-proton proximities in the solid state

The wide applicability of H solid-state NMR experiments that directly probe proton-proton proximities is presented. The power of NMR as a site-specific probe of structure and dynamics is principally a consequence, on the one hand, of the chemical shift by which different chemical environments are distinguished and, on the other hand, the coupling of nuclear spins so as to reveal through-bond connectivities or through-space proximities via dipolar couplings, respectively. Fast MAS or homonuclear decoupling allows structurally or dynamically informative high-resolution H-H correlation experiments to be recorded for an increasing number and wide range of rigid-solid applications. Fast MAS and modern rf consoles allow the straightforward implementation and robust and reliable performance of homonuclear decoupling sequences. H-H spin diffusion and 1H multiple-quantum experiments will also become increasingly more routine, with application to more complex and larger systems.